[OSM-talk] visitor counter in wiki vanished

[Tom Hughes]

On 03/05/10 14:51, Peter Körner wrote:
> Gary G: schrieb:
>> from my point of view this is a very weak argument - assuming that of course counting an integer value and sometimes "print" it does not consume too much ressources - how many bytes can it be? probably there are other, more promising potentials?
>
> In theory you're right but it's a quuestion of how efficient the
> wikimedia plugin-system and the actual counter plugin is implemented.

It's not a plugin as far as I know, it's a core feature of mediawiki. 
You will note however that it is turned off on wikipedia itself for 
exactly the same reason that we have turned it off.

The counter is held in the database - it has to be somewhere where all 
the different server processes can access it so it's not just a matter 
of incrementing a variable in memory as Gary seems to suggest.

That means that every request for a page suddenly gets transformed from 
a read operation on the database, which can run at the same time as 
other read operations, into a write operation which needs to lock rows 
in the hit counter table while it updates the counter. That leads to 
lock contention between the server processes at times of high load.

Tom

-- 
Tom Hughes (tom at compton.nu)
http://compton.nu/